1. Field of the Invention
This invention generally relates to an A/D converter with adjustable internal connection and a method for operating the same, and more particularly to an A/D converter with adjustable internal connection and a method for operating the same by using a plurality of piezoelectric transformers and the connection of those piezoelectric transformers input terminals are adjustable.
2. Description of Related Art
To reduce the usage of the chemical material, most electrical devices use direct current (DC) sources such as batteries as power sources and thus have A/D converters. Hence, those devices can use the alternating current (AC) sources provided by the electrical power companies. A traditional A/D converter uses a magnetic transformer to obtain a required DC voltage. However, due to the safety standard requirement, the secondary coils of this magnet transformer require a certain amount of distances between adjacent coils. This limitation makes the size impossible to be small. On the other hand, the piezoelectric transformer has the advantage of small size and good insulation. Hence, more and more researches focus on the application of the piezoelectric transformer. However, because the voltage standards adopted by different countries are different, an A/D converter with a single piezoelectric transformer cannot be universally used all over the world.
To resolve this problem, some manufacturers provide an improved A/D converter, which uses an active-clamp half-bridge circuit, pulse frequency modulation (PFM) and pulse width modulation (PWM) feedback controller to respond the different voltage input. However, the design of the controller is very complicated and costly, and thus cannot be adopted for mass-production.